Relative dating of the earth
For GPS satellites to work, they must adjust for similar bending of spacetime to coordinate with systems on Earth.
According to the theory of relativity, time dilation is a difference in the elapsed time measured by two observers, either due to a velocity difference relative to each other, or by being differently situated relative to a gravitational field.
For sufficiently high speeds, the effect is dramatic.
Space travelers could then return to Earth billions of years in the future.
Such time dilation has been repeatedly demonstrated, for instance by small disparities in a pair of atomic clocks after one of them is sent on a space trip, or by clocks on the Space Shuttle running slightly slower than reference clocks on Earth, or clocks on GPS and Galileo satellites running slightly faster.
Special relativity indicates that, for an observer in an inertial frame of reference, a clock that is moving relative to him will be measured to tick slower than a clock that is at rest in his frame of reference.
If two persons A and B observe each other from a distance, B will appear small to A, but at the same time A will appear small to B.
Common sense would dictate that, if the passage of time has slowed for a moving object, said object would observe the external world's time to be correspondingly sped up.It is not possible to make the speed of light appear greater by moving towards or away from the light source.Consider then, a simple clock consisting of two mirrors relative to the resting frame of the clock (diagram at right), the light pulse is seen as tracing out a longer, angled path.A scenario based on this idea was presented in the novel Planet of the Apes by Pierre Boulle, and the Orion Project has been an attempt toward this idea.
With current technology severely limiting the velocity of space travel, however, the differences experienced in practice are minuscule: after 6 months on the International Space Station (ISS) (which orbits Earth at a speed of about 7,700 m/s) an astronaut would have aged about 0.005 seconds less than those on Earth.This case is sometimes called special relativistic time dilation.The faster the relative velocity, the greater the time dilation between one another, with the rate of time reaching zero as one approaches the speed of light (299,792,458 m/s).This causes massless particles that travel at the speed of light to be unaffected by the passage of time.